Process for finishing steel bars

ABSTRACT

The process of the invention comprises a treatment for roughturned hot-rolled or hot-finish steel bars to provide a defectfree finished product. The process of the invention serves to remove maximum stock from a straightened bar and to finish the surface of the bar in one complete operation from hot-rolled stock. The finished product is completely free from surface defects, and is rust inhibiting and ready for use without the need for any surface machining, or the like.

[ Aug. 7, 1973 United States Patent 11 1 Elman 1/1954 Peterson...............................5l/324 11/1964 Shaw et al.

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rough-turned hot rolled or hot-finish steel bars to provide a defect-free finished product. The process of the invention serves to remove maximum stock from a straightened bar and to finish the surface of the bar in ENTS one complete operation from hot-rolled stock. The finished product is completely free from surface defects, and is rust inhibiting and ready for use without the need for any surface machining, or the like.

1 Claim, 1 Drawing Figure r me a" eu SF 3388 299 9988 1111 044 ll PROCESS FOR FINISHING STEEL BARS BACKGROUND OF THE INVENTION It is usual in the first step in the prior art production of steel bars to form the bars by a hot-rolling process which involves treating the metal of the bars at temperatures above its recrystallization temperature. Since no strain loading results, relatively greater diameter reduction and resulting economic advantages may be obtained by such a hot-rolling process, as compared with a cold-rolling process. However, oxidation occurs on the surface of the bars formed by the hot-rolling process, and this leads to surface scale formation, and to other surface defects. A surface fiber structure also results on the bars from the hot-rolling process and due to alignment of non-metallic foreign materials in the rolling direction.

The usual prior art practice in the finishing of hotrolled steel bars, as mentioned above, is to subject the bars to a pickling solution which removes as much of the surface scale as possible, and by then subjecting the bars to a cold drawing process in an attempt to provide an acceptable surface finish. However, the surface defects which remained on the bars after the prior art pickling operation are not removed by the subsequent cold drawing step, but are merely drawn out and elongated. Thus, the finished prior art cold drawn steel bars still exhibits substantial surface defects, and machining is required if these defects are to be sufficiently removed for many purposes. Such machining, however, exposes the surface of the bars to further oxidation in the form of rust, and the like.

The process of the invention obviates the steps previously used in the prior art, whereby the hot-rolled bar is first pickled to remove surface scale and is then colddrawn in an attempt to provide an acceptable finished bar. Contrary to the prior art, the process of the present invention produces a fine finished product in two main steps. The first step of the process comprises straightening the hot-rolled bars under predetermined pressure which serves also to impart certain structural changes and to provide necessary tensile hardness formerly achieved by more complex methods in the prior art. As a second step in the process of the invention, up to 0.70 of the total outer diameter is removed from the straightened bar and the bar is finished to a close precision tolerance by grinding and finishing in one operation thereby imparting a finish to the bar of 10 microinches or better.

In addition, the process of the present invention is simpler and more efficient than the prior art pickling and cold drawing process, and yet it results in a superior product which is produced less expensively than the prior art cold drawing process. Specifically, the use of the process of the present invention results in a reduction of labor costs, a reduction in material costs, and it also results in a substantial reduction in rejects, as compared with the prior art cold drawing process.

BRIEF DESCRIPTION OF DRAWING DETAILED DESCRIPTION OF THE PROCESS OF THE INVENTION The process of the invention is applicable, for example, to various types of steel bars, from A: inch to l3 inches in diameter, including stainless steel, carbon steel, or alloy steel. The process is used in conjunction with hot-rolled steel bars which still have surface scale as a result of oxidation during the hot-rolling process.

As a first step in the process of the invention, the hotrolled bars are subjected to a straightening operation using a predetermined pressure so as to straighten the bars for the second step of the process and also to impart certain structural changes providing necessary tensile hardness to the bars. As mentioned above, the straightening step may bt. carried out, for example, by means of a Blaw-Knox Medart straightener, or its equivalent.

A second step in the process of the invention involves a combined grinding and finishing operation, whereby the straightened hot-rolled bars are subjected to a grinding operation which, for example, is adjusted to remove up to 0.70 of the total outer diameter and to finish the bar to a close precision tolerance, imparting a finish of 10 micro-inches or better in one operation. The second step of the process may be carried out by a servo-mechanized machine such as illustrated in the drawing, the machine consisting, for example, of five heads, comprising two solid wheel heads and three belt sander or grinder heads.

The particular machine illustrated in the drawing is a modified Sundstrand-Engleberg abrasive belt centerless grinding machine which is designed for sizing and finishing bars of all grades of stainless steel, carbon steel, alloy steel, tool steel, aluminum, titanium and other materials, of from 1% inch 13 inch diameter.-

The particular machine illustrated in the drawing comprises a series of load arms I which are electrically interlocked with a release lever S to deposit one bar at a time on a plurality of powered outboard support rolls. A plurality of screw jacks 2 power a load table 3 up or down in a pivotal movement from, for example, l to +3. The bar diameter determines the angular setting of the load table. An adjustable stop 4 provides a positive stop for the stored bars, the stopping adjustable in a vertical plane for various diameters of the bars. The release lever 5 provides automatic release of only one bar at a time onto the load arms 1, and it is adjustable for various diameters of the bars.

A plurality of heads 6 and 6a are provided. As mentioned above, for example, three of the heads 6a are of the abrasive belt type for finishing purposes, and two of the heads are of the solid wheel type for performing the grinding operation. The abrasive belt heads 6a may, for example, be 12 inches wide by 144 inches long, whereas the grinding wheel heads 6 comprise grinding wheel sizes exhibiting an l8 inch face and a 24 inch diameter, and driven by 1,000 horsepower motors in a constructed embodiment. The heads 6 and 6a are of a heavy cast construction and are retractable. The grinding heads 6 are located on hardened and ground ways and are positionable. The abrasive belt finishing heads are utilized, for example, along abrasive belts of the aforesaid dimensions in conjunction with reversible contact wheels. The aforesaid hardened and ground ways are designated 7 in the drawing.

Tapered, nose-hardened and precision ground grinding spindles 8 are straddle mounted on dual inboard and outboard bearings. Drive motors 9 are mounted on the individual grinding and finishing heads 6 and 6a and move with the heads. Load/unload table rails 10 are provided. The unload table 11 may be made of heavy duty rectangular tubing. Unload arms 12 are provided, and when the end of a bar being processed passes a proximity switch, the unload arms remove the bar from the powered outboard support rolls and deposit it on the unload table 11.

. A variable speed drive 13 powers both sets of outboard support rails, and the drive is synchronous with that of the wheel drives 19, and with the exit powered outboard support 23. The powered outboard support 23 is the same as the entrance support. The powered outboard support utilizes heavy duty rectangular tubing, as shown.

Series of powered feed rolls 15 are positioned on both the bottom and front side, and are adjustable as a single unit for different power diameters. Powered screw jacks l6 precisely position the front feed rolls. The feed rolls are mounted, for example, on 28 inch centers staggered to provide maximum stability. Automatic oil mist lubrication 17 is provided for the inboard and outboard spindle bearings, for the inboard and outboard idler pulley bearings and for the through-feed jack assembly.

Angulated through-feed fixtures 18 are linked together to provide a unitary adjustment. A single push button station power actuates the fixture for diameter adjustments of the bars being processed of, for example, 1 inch 13 inches. An angulated type movement eliminates the need for several work rest blades, and only one bladeis required to handle bar diameters from 1 inch to 10 inches.

Unitary adjustment allows exact positioning of all regulating wheel slides 19 simultaneously by a single push button control. The regulating wheels are straddle mounted between dual inboard and outboard bearings.

Intermediate head guides 20 are provided for guiding the bar being processed as it moves between the heads 6 and 6a. All the intermediate head guides are positioned as a single unit by means of a push button control. These guides consist of rolls mounted on adjustable beams which are power positioned in a linear path. Precision screw jacks 21, which are power actuated, locate the heads 6 and 6a to adjustable dial control setting.

The illustrated mechanism described above may be servo controlled by means of a digital read-out servo system to provide complete change-over for the machine from one diameter of bar to another in a relatively short time.

It should be pointed out that the mechanism described above, together with an appropriate servo control, is a commercially available item, as manufactured, for example, by Sundstrand-Engleberg, Inc. of Syracuse, New York. This machine represents but one appropriate commercially available mechanism for practicing the invention, and it is believed that a more detailed description of the machine is unnecessary for a full and precise understanding of the process of the invention.

The second step of the process of the invention may be carried out by the machine shown in the drawing which, for example, initially grinds the bars to remove up to 0.070 total outer diameter, and also serves to finish the bars to a close precision tolerance, imparting, for example, a finish of 10 micro-inches, or better in one operation. The finished bar, treated in accordance with the process of the invention, is a superior product as compared with the prior art cold drawn steel bar, and yet the process of the invention is simpler and less expensive to carry out than the prior art process. The finished bar may be passed through a sizing die and, in some instances, formed into a coil.

It will be appreciated that although a particular embodiment of the process of the invention, and of a suitable mechanism for carrying out the process, have been described, modifications may be made. It is intended to cover the process of the invention and all modifications which come within the scope of the invention in the following claims.

What is claimed is:

l. A process for treating a hot-rolled steel bar having surface scales thereon as a result of oxidation during the hot-rolling process, and which comprises: initially straightening the steel bar under predetermined pressure to impart enhanced tensile hardness thereto, and grinding the surface of the steel bar to remove substantially 0.70 per cent of the total outer diameter so as to remove the scale and surface defects and to provide a finish on the surface of the bar of the order of 10 microinches or less.

l l I i l 

1. A process for treating a hot-rolled steel bar having surface scales thereon as a result of oxidation during the hot-rolling process, and which comprises: initially straightening the steel bar under predetermined pressure to impart enhanced tensile hardness thereto, and grinding the surface of the steel bar to remove substantially 0.70 per cent of the total outer diameter so as to remove the scale and surface defects and to provide a finish on the surface of the bar of the order of 10 micro-inches or less. 